PSLE
A book shop is having a book sale. The 1st book is at 5% discount. The 2nd book is at 15% discount. The price of the 2nd book should be equal or lower than the price of the 1st book.

1. Erika's books were priced at $6 and $10. How much more did she pay for the 1st book than the 2nd book? 
2. Fred paid a total of $55.35 for his two books. He paid $11.15 more for the 1st book than for the 2nd book. What was the price of the 1st book before discount? 

	1st book	2nd book	Total amount
Original price	100% $10	100% $6
Discount	- 5%	- 15%
Sale price	95%	85%	?

(a)
Selling price of the 1st book
= 95% x 10
= ⁹⁵₁₀₀ x 10
= $9.50

Selling price of 2nd book
= 85% x 6
= ⁸⁵₁₀₀ x 6
= $5.10

Amount that Erika paid more for the 1st book than the 2nd book
= 9.50 - 5.10
= $4.40

	1st book	2nd book	Total amount
Original price	100%	100%
Discount	- 5%	- 15%
Sale price	95%	85%
Compare 1st book and 2nd book	1 u + $11.15	1 u	$55.35

(b)
Sale price of the 1st book = 1 u + 11.15
Sale price of the 2nd book = 1 u

Total amount that Fred paid
= 1 u + 11.15 + 1 u
= 2 u + 11.15

2 u + 11.15 = 55.35
2 u = 55.35 - 11.15
2 u = 44.20

1 u = 44.20 ÷ 2 = 22.10

Sale price of the 1st book
= 1 u + 11.15
= $33.25

95% of the price = $33.25
100% of the price = ^33.25₉₅ x 100 = $35

Selling price of the 1st book before discount = $35

Answer(s): (a) $4.40; (b) $35